Conventionally, polyimide has been widely used as surface protection films or interlayer insulating films because of its advantages in resistance to heat, mechanical property and electric property, as well as easy film formability and planarizability of film surface.
When polyimide is used as the surface protection film or the interlayer insulating film, a forming process of through holes is performed by an etching process usually with the use of positive type photoresists. However, this forming process includes application and removal of the photoresists, and is therefore complicated. Thus, heat resistant materials having photosensitivity have been investigated for the purpose of streamlining works in this forming process.
Concerning photosensitive polyimide compositions, a polyimide precursor composition in which a photosensitive group has been introduced by an ester bond (this composition is referred to hereinbelow as the composition (1). See, e.g., Patent Document 1), and a composition of a polyamide acid added thereto a compound having a carbon-carbon double bond which is dimerizable or polymerizable upon receiving a chemical ray and an amino group and a compound containing an aromatic bisazide (this composition is referred to hereinbelow as composition (2). See, e.g., Patent Document 2) have been known and used.
When the photosensitive polyimide composition is used, typically a pattern is formed by applying the composition in a form of solution onto a substrate and then drying it, irradiating active light through a mask, and removing an exposed portion by a developing solution.
The aforementioned compositions (1) and (2) are negative type compositions which require an organic solvent as the developing solution. The developing solution composed of the organic solvent gives a heavy adverse impact on environment when discarded as liquid waste. Thus, in the light of recent environmental concern, now there is a demand for photosensitive heat resistant materials capable of being developed by an aqueous developing solution which is easily wasted. Further, in order to switch from the etching process using the positive type photoresist to the negative type photosensitive polyimide, it is necessary to change the mask in an exposure apparatus and the development equipment. The compositions (1) and (2) have the aforementioned problems.
Meanwhile, as the positive type photosensitive polyimide, a polyimide precursor in which an o-nitrobenzyl group is introduced by an ester bond (this composition is referred to hereinbelow as precursor composition (3). See, e.g., Patent Document 3), and a composition comprising phenolic hydroxyl group-containing polyamide acid ester and an o-diazoquinone compound (this composition is referred to hereinbelow as composition (4). See, e.g., Patent Document 4) have been known. As a positive type heat resistant material, a composition comprising a photosensitizer material using polybenzoxazole having heat resistance, mechanical property and electric property equivalent to those in polyimide, a polybenzoxazole precursor and an o-diazoquinone compound (this composition is referred to hereinbelow as composition (5). See, e.g., Patent Documents 5 and 6) has been known.
However, the precursor composition (3) has low sensitivity because its sensitive wavelength is mainly 300 nm or less. In particular, it is difficult to use the composition (3) with i-line stepper (single wavelength light at 365 nm) which is recently used. The compositions (4) and (5) have more sensitive than the precursor composition (3), but their sensitivity is insufficient for practical use. On the contrary, there is known a composition in which phenol binuclear compound is added aiming at enhancing the sensitivity (the composition is referred to hereinbelow as composition (6). See, e.g., Patent Document 6). However, when the phenol binuclear compound is added as in this composition (6), the pattern is easily deformed by melting of the phenol compound in a thermal cure process after the development, which results in a problem such as a degradation of resolution. Thus, it is difficult to provide the photosensitive polymer composition which has the sufficient sensitivity and which does not cause the pattern deformation in the thermal cure process after the development.    Patent Document 1: JP S55-30207    Patent Document 2: JP H03-36861 B    Patent Document 3: JP S60-37550 A    Patent Document 4: JP H04-204945 A    Patent Document 5: JP S64-6947 A    Patent Document 6: JP H09-302221 A